The invention relates to fasteners for splicing ends of conveyor belts together and applicators therefor and, more particularly, to conveyor belt fasteners having rivets pre-inserted thereto and an apparatus and method for securing pre-inserted rivet fasteners to belt ends.
To join two belt ends together, mechanical belt fasteners are typically used either of the hinged type where the individual fasteners have upper and lower plates joined by arcuate loops for mating with the loops of identical hinged fasteners on other belt ends or the solid plate type where the upper and lower plates span the joint between the two belt ends to be spliced together. In both cases, the plates have apertures therein that are aligned when clamped on respective upper and lower surfaces of the belts so that fastener members, e.g. rivets, staples, can be installed through the apertures and the belt for securing the belt fasteners to the belt ends. Conveyor belts having these types of splices in place can be used in a wide variety of applications depending on the materials being conveyed and the stresses applied to the splice during conveyor belt operations.
To assist in installation of rivets to belt fasteners with the rivets extending through the carcass of the conveyor belt, pilot nails have been utilized attached to a lower, hollow end portion of the rivet, such as shown in U.S. Pat. No. 3,913,180, commonly assigned to the assignee of the present invention. The pilot nails fit through an aperture in the upper plate and pierce the underlying upper surface of the belt and lead the attached rivets through the belt until the lower, hollow end of the rivet projects through the lower plate aperture for being upset thereat to form a flared rivet head at the bottom of the rivet shaft. After the bottom rivet head is formed, the nail is released from being held in the hollow end of the rivet and is caught in the applicator tool. This creates the problem of what to do with the mess created by the separated pilot nails as well as complicating the application process.
There have been various application tools developed for installing riveted belt fasteners to belt ends. Applicants"" assignee herein has tools for users that allow individual rivet and pilot nails assemblies to be driven as well as those that can gang drive several of these assemblies simultaneously such as for larger rivet fasteners that utilize several rivets for an individual fastener. The present invention is not limited to the number of rivets used with a fastener. An applicator tool for rivet fasteners is shown in applicants assignee""s co-pending U.S. patent application, Ser. No. 09/177,238, whose disclosure is incorporated as if reproduced in its entirety herein. In each instance, the rivets and nails have to be loaded into a shaft of the tool aligned over the apertures of the plates for driving therethrough. This can create undesirable delays in the installation process for splicing belt ends using rivet belt fasteners.
For splice strength using riveted fasteners, it is very important that the heads of the rivet are properly formed. Further, in applications where the conveyor belts are used for agricultural equipment such as round hay balers and net wrapping hay balers, it is very important to maintain a low profile for the fastener secured on the belt end. To this end, the rivet heads should be seated in the recessed apertures of the plates so they do not project over the top thereof as otherwise the projecting portions of the head may catch or snag on the net wrapping about the bales. These agricultural applications also tend to be very abusive on the splice in terms of the high-tension forces they are exposed to and the relatively small diameter pulleys, e.g. 3 to 3.5 inches in diameter, about which they must travel. To make the fasteners stronger, larger, thicker plates can be utilized along with greater numbers of rivets. However, this raises the costs for the fastener and is a detriment to their ability to travel about small sized pulleys. Thus, one option is to reduce the size of the plate by keeping it relatively thick and lowering the number of rivets used therewith. In this instance, proper forming of rivet heads becomes extremely important as there are fewer rivets holding the plates onto the belt ends.
Accordingly, there is a need for a rivet fastener that can be installed to belt ends with greater ease and speed, and an application tool for this purpose. Further, a rivet fastener that is relatively small in size but provides relatively high strength is needed.
In accordance with the present invention, a fastener for splicing ends of conveyor belts together is provided having a rivet that is pre-inserted to provide speed and ease in installation. Although one rivet per fastener is illustrated and described, one or more rivets can be pre-inserted on an individual fastener in accordance with the teachings of the invention herein. In the context of the present invention, the term xe2x80x9cpre-insertedxe2x80x9d refers to the rivet being held in the plate aperture so that the rivet is carried by the plate before the installation process commences. The pre-inserted rivet preferably is held by an interference fit in the plate aperture as described hereinafter, although the rivet could be held by other mechanisms such as by an adhesive between the rivet and aperture.
As mentioned above, the rivet can be held in an aperture of the upper plate by an interference fit at the lower end thereof. Preferably, the interference fit is achieved by knurling of the lower end portion of the rivet shaft to create raised interference portions or ridges integral therewith that are sized to be in an interference fit in the upper plate aperture. The remainder of the shaft can be sized to provide clearance between it and the aperture. In this manner, during driving of the rivet, after the interference portions clear the upper plate aperture, the rivet is no longer in press-fitting engagement therewith. This avoids scraping of the rivet shaft by the edges about the upper plate aperture minimizing damage to the rivet body and so that the softer metal material of the rivet is not pushed up under the head preformed at the upper end thereof as might otherwise prevent the upper rivet head from seating fully in the recessed aperture of the upper plate. Further, with the upper rivet head properly seated in the upper plate recessed aperture, the amount of material at the lower end of the rivet for being upset is sufficient for proper forming of the lower rivet head to increase the holding strength of the rivet. In a preferred form where only a single rivet is used to secure the fastener to the belt, the ability to properly form and seat the rivet heads for providing good holding power is of particular importance.
Accordingly, and in one form of the invention, a fastener for splicing ends of conveyor belts together is provided including upper and lower plates for being clamped on respective upper and lower surfaces of the conveyor belt. Apertures of the plates are generally aligned with each other with the plates clamped on the belt. A rivet is provided having a shaft with an end portion thereof held in an upright, pre-inserted position in the aperture of the upper plate prior to riveting of the fastener to the belt end. Interference portions integral with the shaft end portion are sized to be in an interference fit in the upper plate aperture. Thus, the present fastener avoids the need for loading rivets into a shaft of an applicator tool speeding installation time.
The interference portions can include raised ridges having an interference diameter larger than the aperture diameter. Preferably, the rivet shaft has a clearance diameter and includes a preformed enlarged head at one end thereof. The interference diameter of the raised ridges is larger than the clearance diameter so that after the held rivet portion is driven through the upper plate aperture, the shaft clears the aperture to minimize scraping and pushing of material of the rivet along the shaft thereof up under the preformed rivet head. Where the upper plate includes a recess about the aperture, the preformed enlarged rivet head is fully seated to provide a low profile riveted fastener. This is desirable in terms of avoiding problems with materials or items conveyed on the belt, e.g. net wrap hay bales. In addition, the seating of the rivet head in the recessed aperture allows an upset head at the bottom of the rivet shaft to be properly formed thereat.
In one form, the rivet portion includes a tubular wall portion and a hollow bore to receive a pilot therein to lead the rivet through the belt. The hollow tubular portion is adapted to be flared to form an upset head in the lower plate aperture.
In a preferred form, the rivet is a single rivet used with the plates for clamping to the belt and there is at least one arcuate hinged loop joining the upper and lower plates with the loop and plates having a predetermined substantially constant material thickness in cross-section and a predetermined width. The ratio of the predetermined thickness to width is sized to provide small, heavy-duty hinged fastener riveted to a belt by the single rivet.
In another form of the invention, a rivet hinged belt fastener for splicing of belt ends together is provided including a pre-inserted rivet including a shaft thereof held in the aperture of the upper plate and an enlarged preformed head at one end of the shaft above the upper plate. A tubular portion of the shaft is adapted to be flared into a rivet head and held in the upper aperture to provide a pre-inserted hollow rivet on the upper plate. Preferably, the tubular portion of the rivet shaft is sized to be held by an interference fit in the upper plate aperture.
In one form, the rivet shaft includes a solid portion below the head sized to clear the upper plate aperture during driving of the rivet therethrough to allow the rivet preformed head to seat substantially flush in the upper plate recessed aperture. As stated, the present pre-inserted rivet fastener provides a low profile so that the upper head does not catch on wrapping of hay bales when used in agricultural applications, and an upset head can be properly formed at the lower end of the rivet for seating in the recessed aperture of the lower plate.
In a preferred form, the shaft tubular portion is knurled to form integral outwardly projecting larger diameter portions tightly gripped in the aperture of the upper plate. In this manner, the shaft of the rivet can be provided with the larger diameter portions in a secondary operation after forming of the rivet body without removal of material therefrom.
In another aspect of the invention, an apparatus for installing fasteners having a pair of plates with apertures therein on ends of conveyor belts is provided. The apparatus includes a frame, and a plurality of operating members mounted to the frame. A positioning member is provided between the operating members for placing the fasteners and beltin predetermined positions relative to each other with the belt end projecting between the fastener plates. A camming mechanism shifts the operating members in a transverse direction relative to the belt. Rivets of the fasteners are driven by first one of the operating members on one side of the belt for clamping the fastener to the belt end. Pilot nails are aligned with the rivets driven by a second one of the operating members on an opposite side of the belt to pierce the belt. An actuator cooperates with the camming mechanism to coordinate the shifting of the operating members for driving the rivets and nails so that the nails are first driven through the belt to the aligned rivets and the rivets together with the nails are then driven back through the belt with the rivets being led by the pilot nails therethrough. The present apparatus is especially well adapted for use by original equipment manufacturers (OEMs) that have to install large volumes of belt splices on a regular basis.
In one form, the rivets include a tubular end portion pre-inserted into the aperture of one of the plates of the fastener, and the nails are driven through the aperture of the other plate and the belt into registry with the rivet tubular end portion. Because the nails are not separably attached to the rivets as in the previously-described rivet and nail assemblies, the nails can be designed for reuse thereby eliminating the problem of having to deal with the nails as scrap and the time and costs associated therewith.
Preferably, the actuator is a power actuator that has a predetermined driving stroke in a longitudinal direction that is larger than the distance the actuator causes operating members to shift to provide a mechanical advantage in driving of the rivets and nails.
In one form, the camming mechanism includes cam followers of the operating members that are substantially fixed against shifting in the longitudinal direction, and cam tracks in which the followers are disposed for shifting the operating members in the transverse direction as the tracks are shifted in the longitudinal direction by the actuator. In this manner, the camming mechanism converts the longitudinal motion of the cam tracks vis-a-vis the actuator into transverse motion of the operating members and the rivets and nails driven thereby.
In a preferred form, the camming mechanism includes a rack having the cam tracks and the actuator is a single power cylinder which shifts the rack and cam tracks in the longitudinal direction to shift the operating members in the transverse direction by a single driving stroke of the cylinder. Accordingly, the entire riveting operation from piercing the belt with the pilot nails to driving of the rivet and nails occurs by way of one driving stroke of the power cylinder.
In one form, one of the operating members includes an anvil surface and the pilot nail includes a rivet curling surface. The camming mechanism is operable to shift the second operating member to bring the rivet curling surface into cooperation with the anvil surface. The second operating member then pauses while the first operating member continues to shift to push the rivet against the curling surface and to the anvil surface for forming an upset head on the rivet. As is apparent, the camming mechanism provides highly coordinated shifting of the various operating members to properly form rivets for securing fasteners to belt ends.
Preferably, the third operating member is a clamping and anvil member shifted by the camming mechanism to clamp the fastener plates on surfaces of the belt at the end thereof. An adjustment screw is operable to shift the second and third operating members together relative to the frame to allow for different thicknesses of belts to be riveted.
In yet another aspect of the invention, a method of securing a belt fastener having a pre-inserted rivet thereon to a belt end is provided. The method includes placing a belt end including upper and lower surfaces between upper and lower plates of a plurality of fasteners with the pre-inserted rivets on one of the upper and lower plates, causing pilots to be driven through apertures of the other of the upper and lower plates and through the adjacent belt surface and then into hollow bores in tubular rivet ends of the pre-inserted rivets, driving the pre-inserted rivets through the apertures of the one plates with the hollow rivets following the previous path of the pilots, and forming the tubular ends of the rivets into flared-shaped rivet heads at the other plates to secure the belt fasteners to the belt end.
The pilots can be nails including sharp leading points thereof and the method can further include spreading material of the belt by driving of the pilot nails therethrough from the belt lower surface to the belt upper surface and into the rivet bores to minimize belt material punched out by the rivets as they are driven and led back through the belt by the pilot nails. In this manner, a good, strong splice is formed as damage to the carcass of the belt is minimized which would otherwise occur if the rivet was tearing into the belt carcass as it was being driven therethrough. After the fastener is riveted to the belt end, the belt material tightly grips about the shaft of the rivet with little or no loose play therebetween. Further, because the belt material is spread, there is no punching of belt material or slugs therefrom, and thus there are no pieces of belt that have to be cleaned from around the tool.